Soliton fibre lasers mode-locked at a high harmonic of their round-trip frequency have many potential applications, from telecommunications to data storage(1). Control of multiple pulses in passively mode-locked fibre lasers has, however, proved very difficult to achieve. This has recently changed with the advent of fibre lasers mode-locked by intense optomechanical interactions in a short length of photonic crystal fibre(2,3). Optomechanical coupling between cavity modes gives rise to highly stable, optomechanically bound, laser soliton states. The repetition rate of these states corresponds to the mechanical resonant frequency in the photonic crystal fibre core(4), which can be a few gigahertz. Here we show that this system can be successfully used for programmable generation and storage of gigahertz-rate soliton sequences over many hours

Harmonic mode‐locking (HML) is an important technique enabling the generation of high‐repetition‐rate ultrashort pulses. Using an emerging time‐stretch dispersive Fourier transform technique, the experimental observation of the entire buildup process of the passive HML state in an ultrafast fiber laser is reported here. It is unveiled that the whole process of HML buildup successively undergoes seven different ultrafast phases: raised relaxation oscillation, spectral beating behavior, birth of a giant pulse, self‐phase‐modulation‐induced instability, pulse splitting, repulsion and separation of multiple pulses, and a stable HML state. It is observed that the multiple HML pulses originate from a single‐pulse splitting phenomenon and a remarkable breathing behavior occurs at an early stage of the HML buildup process. The numerical results confirm that the effects of dispersive wave, gain depletion and recovery, and acoustic wave play key roles in the earlier, middle, and later stages of this HML buildup process, respectively; as well, the acoustic resonance in the single‐mode fiber stabilizes the final HML state of lasers.

Self-assembly of fundamental elements through weak, long-range interactions plays a central role in both supramolecular DNA assembly and bottom-up synthesis of nanostructures. Optical solitons, analogous in many ways to particles, arise from the balance between nonlinearity and dispersion and have been studied in numerous optical systems. Although both short- and long-range interactions between optical solitons have attracted extensive interest for decades, stable soliton supramolecules, with multiple aspects of complexity and flexibility, have thus far escaped experimental observation due to the absence of techniques for enhancing and controlling the long-range inter-soliton forces. Here we report that long-range soliton interactions originating from optoacoustic effects and dispersive-wave radiations can be precisely tailored in a fibre laser cavity, enabling self-assembly of large numbers of optical solitons into highly-ordered supramolecular structures. We demonstrate several features of such optical structures, highlighting their potential applications in optical information storage and ultrafast laser-field manipulation.

AimThe aim of this study is to assess the depression of pregnant women in the aftermath of an earthquake, and to identify the social support that they obtained, their coping styles and socio-demographic factors associated with depression.MethodsA total of 128 pregnant women from three hospitals in the epicenter area were recruited immediately after the Ya’an earthquake. Their depression was investigated using the Edinburgh Postnatal Depression Scale (EPDS) with a cutoff score of 14; the social support that they obtained was measured using the Social Support Questionnaire; and their coping styles were assessed using the Coping Styles Questionnaire.ResultsImmediately after the earthquake, the incidence rate of depression in pregnant women was 35.2%, higher than that of the general pregnant population (7%-14%). The EPDS scores were significantly correlated with gestation age at the time of the earthquake, objective support, subjective support, use of support, negative coping style, and positive coping style. The regression analysis indicated that risk factors of prenatal depression include the number of children, relatives wounded, subjective support, and coping styles. A further analysis of the interaction between social support and two types of coping styles with depression showed that there was interaction effect between subjective social support and positive coping styles in relation to EPDS scores. There was an inverse relationship between low EPDS scores and positive coping styles and high social support, and vice versa.ConclusionThe timing of the occurrence of the earthquake may not necessarily affect the progress of the illness and recovery from depression, and psychological intervention could be conducted in the immediate aftermath after the earthquake. The impact of coping styles on prenatal depression appeared to be linked with social support. Helping pregnant women to adopt positive coping styles with good social support after a recent major earthquake, which is a stressor, may reduce their chances of developing prenatal depression.

Ultrafast lasers with high repetition rates are of considerable interest in applications such as optical fiber telecommunications, frequency metrology, high-speed optical sampling, and arbitrary waveform generation. For fiber lasers mode-locked at the cavity round-trip frequency, the pulse repetition rate is limited to tens or hundreds of megahertz by the meter-order cavity lengths. Here we report a soliton fiber laser passively mode-locked at a high harmonic (similar to 2 GHz) of its fundamental frequency by means of optoacoustic interactions in the small solid glass core of a short length ( 60 cm) of photonic crystal fiber. Due to tight confinement of both light and vibrations, the optomechanical interaction is strongly enhanced. The long-lived acoustic vibration provides strong modulation of the refractive index in the photonic crystal fiber core, fixing the soliton spacing in the laser cavity and allowing stable mode-locking, with low pulse timing jitter, at gigahertz repetition rates. (C) 2015 Optical Society of Americ

Abstract:We report the results of our preliminary investigation on the use of hollow-core photonic bandgap fiber (HC-PBF) for hydrophone application. The response of the commercial HC-1550-02 fiber to acoustic pressure, in terms of normalized responsivity (NR), is measured to be -334.4dB re 1µPa -1 . This agrees well with the theoretically predicated value of -331.6dB re 1µPa -1 and is about 15dB higher than that of the conventional fiber (HNSM-155). With straightforward fiber structure modifications (thinner outer silica cladding and higher air-filling ratio of inner microstructured cladding), the NR could be further enhanced to310dB re 1µPa -1

Among the factors that influenced the mental health of pregnant and postpartum women after earthquakes, family function appears to be one of the most important and deserves further exploration. Other mental health conditions such as minor psychiatric disorders should also be studied for their relationship with disasters and pregnancy. Well-designed studies are needed to enable a better understanding of the relationship between earthquakes and the mental disorders of peripartum women so that the most appropriate interventions can be proposed.

We observed narrow-linewidth lasing spikes in a coherent Brillouin random fiber laser, which uses a continuous-wave fiber laser as the pump source. In this random laser configuration, stimulated Brillouin scattering in a section of conventional single-mode fiber acts as the gain mechanism, while Rayleigh scattering in another section of the nonuniform fiber provides randomly distributed feedback. Above the lasing threshold, coherent random lasing spikes, with a linewidth of ~10 Hz, are measured at the top of the Brillouin gain spectrum. It results from high quality coherent resonance of the Brillouin Stokes light in this open laser cavity.